Compounds of carbon are defined as chemical substances containing carbon. More compounds of carbon exist than any other chemical element except for hydrogen. Organic carbon compounds are far more numerous than inorganic carbon compounds. In general bonds of carbon with other elements are covalent bonds. Carbon in its diamond form is used in jewellery. But diamonds are also used for industrial purposes. It is the hardest substance known to man, and so has many uses in manufacturing processes. Amorphous carbon is used to make inks and paints.